Caption: Antibody and cancer. Computer illustration of an antibody seen with a scanning electron micrograph (SEM) of a cancer cell (orange). The Y-shaped antibody (immunoglobulin) molecule is a protein. It is produced by B-lymphocyte white blood cells as part of an immune response. Its "limbs" (upper & lower left) bind to antigens such as surface proteins on the abnormal cells in cancers. Bound cells are more easily digested by macrophage white blood cells. Bound antibodies also trigger proteins from the immune system's complement system. The proteins cut holes in the cell membrane of abnormal or foreign cells causing them to disintegrate.